Re: BIG counterpoise

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Mark,

On 8 Dec 2002, at 21:59, Tesla list wrote:

 > Original poster: "Mark Broker by way of Terry Fritz 
<twftesla-at-qwest-dot-net>" <mbroker-at-thegeekgroup-dot-org>
 >
 > I have a similar grounding issue.  The coil I built and left my
 > physics department has gone through 2 transformers, with properly
 > set safety gaps and TerryFilter.  (Ok, so the ground wasn't
 > attached to the TerryFilter the last time.)  The coil is 6"
 > secondary with 15/90 input, SRSG, LTR MMC (Panasonics - long before
 > the GeekMMC).  It is run almost exclusively on the third floor of
 > the physics department on the inner "square" of the building
 > (surrounded by classrooms, offices, or a hallway).  I've used
 > mainly a cold water pipe for RF ground, which seems to work, though
 > I have no clue if the pipe is metal all the way to the ground.
 > I've also used a big flexible steel conduit that was housed the
 > lab power supply feeds from the monster regulated power supply in
 > one of the back rooms.  There was no performance difference between
 > the two.
 >
 > Running a long dedicated ground out a window isn't an option for a
 > variety of reasons.  The best option is a counterpoise.  But I'm
 > concerned that the concrete floor 40 feet above soil will be a good
 > enough reference point to keep the counterpoise voltage
 > sufficiently low.  I'd hate to lose another transformer or even the
 > spark gap motor due to excessive ground potential....
 >
 > Mark Broker
 > Chief Engineer, The Geek Group

I've run at 1.5kW or so in a similar environment without losing a
transformer. I earther the secondary to what ever was firmly bolted
to the concrete (the mains ground also participated to some degree
which is why one or two other items with weak/old insulation
succumbed along the way ;) I stopped operating in the room I'd been
using when performance was increased to the point where sparks
threatened to connect with fluoro lights and smoke detectors in the
ceiling. The transformer has just a few inches of lead between its
secondary terminals and the main coil gap. No filters or any other
"protective" gear are included. How long were the leads between your
transformer and the gap?

Regards,
malcolm